Sources tell THR that the price of admission for joining Paramount's sci-fi movie from the "Dark Knight" director was the studio's stake in the classic horror franchise along with its portion of a future "South Park" movie.

When Paramount and Warner Bros. teamed up on Christopher Nolan’s latest movie project, Interstellar, in January, some wondered how Warners made its way on board a project set up at a rival studio.

Now, months later,The Hollywood Reporter has learned more about the price that Warners had to pay in exchange for half the Nolan project. The cast of characters includes Friday the 13th villain Jason Voorhees as well as the foul-mouthed kids from South Park.

Warners, which released Nolan’s megagrossing Batman movies and maintains an overall deal with his Syncopy label, wanted in on Interstellar so badly it gave Paramount its rights to co-finance the next Fridaythe 13th horror film as well as its portion of a future South Park movie. Also part of the deal was an agreement to let Paramount co-finance a to-be-determined A-list Warners property.

Warner Bros. and Paramount declined to comment on the arrangement.

The original Friday was made in 1980 by producer Sean Cunningham with investments from Boston theater owners. Paramount got domestic distribution rights; Warners had international. Eventually, the rights reverted back to Cunningham, who took them to New Line Cinema in the 1990s as part of an attempt to jumpstart a Freddy vs. Jason movie (with the villain from A Nightmare on Elm Street). That process took more than 10 years, and in the meantime, New Line made two other Friday the 13th movies.

When it came time for New Line, now part of Warner Bros., to develop a Friday remake/reboot, it was revealed that Paramount had certain rights to the original and had to be brought in as 50-50 partners. Michael Bay's Platinum Dunes ended up producing 2009's Friday the 13th, which grossed a respectable $91 million for Paramount and Warners on a budget of less than $20 million.

South Park, meanwhile, got its start on Comedy Central, which was formed by a merger of Time Warner’s old Comedy Channel, a spinoff from HBO, and Ha!, created by Paramount’s parent company Viacom.

Despite Warners’ eventual exit from Comedy Central, it retained certain rights to South Park. That explains why Warners had international distribution of the 1999 film, South Park: Bigger, Longer and Uncut, which grossed $83 million on a $21 million budget.

Efforts to launch a sequel to the rebooted Friday as well as a second South Park movie were complicated due to both studios having a share in them. So Warners decided to sacrifice Jason and Cartman for a deal on Nolan's Interstellar, thus maintaining its relationship with the filmmaker and snagging a piece of what could be another Inception.

In the process, risk-averse Paramount got a partner on a pricey sci-fi tentpole in addition to the ability to make another movie based on one of the most successful horror franchises of all time and an animation juggernaut.

However, there is a catch: Sources say Paramount only enjoys the rights for both titles for the next five years and has that amount of time to make follow-up movies.